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An automatic lamp changer (or lampchanger) is a device used to ensure that a navigational light such as a marine lighthouse or aero beacon stays lit even if a bulb burns out. Numerous types exist. The common design elements are an array of two or more lamps (or bulbs), installed on a mounting which can rotate to various positions. Each position brings a different lamp into the focal point of an optical assembly. Since signal and navigational lights use sophisticated optics to focus the beam, lampchangers are designed to position the new bulb at the focal point with high precision. The device automatically detects when the currently active lamp has ceased to function and moves the next lamp into place.
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History
The automatic lampchanger was invented by Charles Wallace and patented in 1928 (patent number unknown). This original model held two headlight lamps from a Model T automobile. The United States Lighthouse Service had these in common use by the 1930s, as they moved to convert all navigational lights to electricity.
CG-2P
The CG-2P, manufactured by Carlisle & Finch. This could be installed in a type DCB-224 aero beacon. It consisted of two bulbs and a mechanism to rotate a fresh bulb into place when the primary bulb has burned out.
CG-4P
There is also a CG-4P type, which contains 4 lamps.
CG-6P
The CG-6P, which contains 6 bulbs in a rotary mechanism. The specification for the CG-6P are described in UC Coast Guard Specification G-SEC-195H, which describes the CG-6P as used to rotate a 12VDC, marine signal lamp of up to 40 watts into the focal position of a U. S. Coast Guard aids to navigation beacon. The power to operating the rotating mechanism comes from a wound spring. The device is required to operate over a temperature range of -25F to +140F, 0% to 100% relative humidity, and be resistant to corrosion from constant exposure to salt air. The stepping mechanism is required to have a means of manual activation, which must be designed to be activated by personnel wearing heavy winter gloves.
Cybernetica AS, in Estonia, makes a version of the CG-6P called the E390. This combines the basic CG-6P mechanism with a remote monitoring system which transmits diagnostic information giving the state of all six lamps.
Other types
Pharos Marine manufactures the model APL1297A. It comes in a number of varieties, with either 4 or 6 bulbs, and running on either AC or DC power.